Under-deposit corrosion (UDC) is a serious problem in oil and gas transmissions lines, tubing, tanks, and separation vessels worldwide that has had a serious impact on pipeline operations and production, and health, safety and environment (HS&E) compliance. Despite the fact that this has been a persistent problem in the industry, there has been little work conducted towards development of a reliable monitoring method for UDC.
UDC is sometimes called “cell corrosion”, and is typically very aggressive and localized, causing deep penetration of the metal surface with lesser general corrosion in the surrounding areas. Due to surface deposits, electrical imbalance or some other initiating mechanism, all corrosion factors attack a select number of individual sites. In some cases, pitting is extended throughout the entire metal surface, giving it an irregular or very rough surface profile. In other instances, pits are concentrated in specific areas, leaving the majority of the metal surface in like-new condition. Galvanized pipe is particularly highly susceptible to UDC.
It is difficult to build a probe where one can ensure that localized corrosion occurs. It would be advantageous if a new sensor or probe were discovered that would be an improvement over the presently known probes and methods for monitoring UDC.